USA officials said they were confident that the incidents were targeted attacks, pointing out that some of the affected diplomats had been staying in a hotel, where none of the hotel workers seem to have been affected.

The secretary said the USA continues to maintain diplomatic relations with Cuba and will continue to cooperate with Cuba on investigatingthe attacks.

"Regarding the attacks, there are now 22 persons medically confirmed to have experienced health effects due to the attacks on diplomatic personnel in Havana".

"It appears that this plays right into the hands of a potential rogue actor - Russian Federation perhaps - that is trying to create a further wedge between our two countries and other nations in the hemisphere", said Rep. Eliot Engel, D-N.Y.

"We are evaluating the impact of the reduction of personnel on these services but the secretary's focus is on the safety and well-being of the diplomatic personnel", the official said.

The warning against travel to Cuba is necessitated, says the statement, because the skeleton staff remaining at the embassy is inadequate to assist USA citizens.

In March, the USA asked two Cuban diplomats to leave the U.S. as a reciprocal measure after two United States diplomats injured in the attacks were unable to return to their posting. The expulsions, the official said, aim to "underscore to the Cubans that they must take more actions to protect our people on the ground".

On Monday, the AP reported that the attacks hit us spies first and they also had the more severe symptoms.

US-Cuban relations expert and Research Associate at the Council on Hemispheric Affairs (COHA), R. O. Niederstrasser, told Sputnik it is obvious that the Trump administration has caved to pressures from the Cuban-American lobby.

The argument is the lack of involvement of the Cuban government in the investigation of the unusual illnesses that have affected the American personnel inside the island.

On Monday, TheAssociated Press reported that USA spies were among the first and most severely affected victims. And waiting times for these procedures can last for months. "And we expect them to leave within seven days".

The removal of 15 will reduce the Cuban staffing to roughly a dozen accredited diplomats.

The US government's decision to expel Cuban diplomats from the United States in retaliation for alleged "sonic attacks" on US personnel in Havana is nothing more than a ploy created to revive the discredited embargo policies of the Cold War era, analysts told Sputnik. That revelation, confirmed to the AP by a half-dozen officials, adds yet another element of mystery to a year-long saga that the Trump administration says may not be over.

While the USA did not directly blame Cuba for the attacks, a State Department official said Cuban officials needed to provide greater assurances that diplomats will no longer be attacked before both countries could resume regular diplomatic operations. The government often uses that designation to expel suspected foreign spies and ensure that they can't come back.

Florida Republican Sen. Marco Rubio, who previously called for the closing of the embassy in Havana, "commended" the State Department for expelling the Cuban diplomats.

Rodriguez criticized what he called "unilateral, unfounded decisions" by Washington.

According to a senior federal official, the USA measure was based on the health incidents reported by US embassy officials in Havana, but stressed that it does not mean a change of policy toward the Caribbean country or assignment of responsibilities for those acts. Extension and entry clearance with a USA passport (only for those who left Cuba before 1970) costa $160.

On Monday, The Associated Press reported that US spies were among the first and most severely affected victims.

Cuban President Raúl Castro (left) shakes hands with former US President Barack Obama, 2015.

President Donald Trump and Secretary of State Rex Tillerson discussed the plan on Monday.